The present invention relates to a chair with a height-adjustable seat, and more particularly, to a chair having an improved mechanism for fastening the seat to a pipe frame.
The inventor has proposed, in Japanese Utility Model Application No. 58838/1984, a chair with a height-adjustable seat, comprising a frame having right and left guides in a pair extending in the vertical, but slightly inclined direction at its both side portions, and a seat movable along the guides and capable of being fixed at any required position for use on the guides.
Each guide of the chair is formed of a pair of pipes or bars, which also serves as a pipe frame of the chair, and each pipe or bar has a circular cross section. The pipes or bars of each guide are arranged at left and right positions in parallel with each other so as to form a longitudinal gap therebetween. Then, the chair has two gaps which are also parallel with each other at both sides thereof.
The seat mentioned above has two supports or brackets having a rear portion freely inserted through the gaps, respectively, and a set of rod-like rear and front stoppers laterally fixed to the rear portions of the supports.
Each stopper comprises a middle portion extending between the supports and outside portions projecting outwardly from the supports. The rear stopper is fixed on the most rear ends of the supports. The front stopper is arranged in parallel with the rear stopper so that the front stopper abuts against the front surface of the guide while the rear stopper abuts against back surface of the guides to grip the guide when the seat is set for sitting.
Further the front stopper is situated lower than the rear stopper, when the seat is set. The whole outer surface of the stoppers are each made of a cylindrical rubber-like elastomeric cover. The covers have a cylindrical shape and are fixed on a core rod so as not to rotate around their axes.
In the above-mentioned chair, the seat is freely movable when the front end portion is taken up to release stopper's gripping force. The user can easily slide the seat upwardly or downwardly, for instance, by gripping the front end of seat and the middle portion of the rear stopper.
When a suitable height is selected, the seat is re-set to a substantially horizontal posture, and then, the front and rear stoppers are abutted against the guide portions, respectively, to grip then. Accordingly, a user's weight is supported by a frictional force between the stoppers and the guide portions. The frictional force increases due to the inclining torque in the front-down direction applied by the user's weight.
However, in the conventional chair, each contacting area between the stopper and the guide portion is narrow, since both stopper and guide portion have cylindrical shapes. That is to say, the guide portion is made of a pair of pipes or bars each having circular cross section since they are also used as a frame of chair as mentioned above. Therefore, there is a disadvantage that stopper's gripping force is not sufficient.
Further, since the middle portions of the stoppers are horizontally bridged between two supports of the seat, rigidity of the outside portions abutting against the outside frame pipes and that of inside portions abutting against the inside frame pipes are different from each other. Therefore, the function as of the as stoppers is not sufficiently effected.
In addition, if the seat is set in a slightly inclined posture in a right and left direction, only one side of the guide portions, i.e. only right or left guide portion is securely caught by the corresponding surfaces of the stoppers, while the other side of the guide portion is not sufficiently caught.
Under such a situation, the gripping forces of left side and right side cannot be in well balance. Accordingly, when a user sits on the seat, one of suppots may occasionally slip down for a small amount. Another disadvantage of the conventional chair is that though the seat can folded upwardly, the seat cannot be securely fixed to the frame when the seat is folded. Therefore, it is inconvenient to carry the folded chair.
One object of the present invention is to provide a chair with a height adjustable seat in which the stopper's function is improved.
Another object of the present invention is to provide a chair in which the seat can be securely fixed to the frame when the seat is folded.